Fluid control devices generally include control valves and regulators. These control devices are usually installed in a fluid process control system such as chemical treatment systems, natural gas delivery systems, etc., for controlling the flow of a fluid through the system. Each control device defines a fluid flow-path and includes a control member for adjusting a dimension of the flow-path. For example, FIG. 1 depicts a known regulator assembly 10 including a valve body 12 and an actuator 14. The valve body 12 defines a flow-path 16 having a narrowed portion or throat 18. The regulator assembly 10 illustrated in FIG. 1 is configured in a flow-up configuration. In other words, fluid flows upward, through the throat 18 as illustrated in FIG. 1.
The actuator 14 includes an upper actuator casing 20, a lower actuator casing 22, and a control member assembly 24. The control member assembly 24 is disposed within the upper and lower actuator casings 20, 22 and is adapted for bi-directional displacement in response to changes in pressure across the regulator assembly 10. Additionally, as is illustrated in FIG. 1, the regulator assembly 10 includes a seat ring 26 disposed in the throat 18 of the valve body 12. The control member assembly 24 cooperates with the seat ring 26 to control the flow of fluid through the throat 18. When the outlet pressure is high, a sealing surface 28 of the control member assembly 24 may sealingly engage the seat ring 26 and close the throat 18. This prevents the flow of fluid through the regulator 10.
The seat ring 26 depicted in FIG. 1 further includes a rounded or tapered surface 27. The rounded or tapered surface 27 serves to streamline the flow of the fluid through an orifice 29. As fluid flows through the valve body 12, it flows from the left of the valve body 12, as depicted in FIG. 1 and up through the throat 18 via the orifice 29 in the seat ring 26. Then, the fluid deflects off a lower surface of the control member 24 including the sealing surface 28, and out to the right of the valve body 12 of FIG. 1.
FIG. 1 illustrates a regulator assembly 10 having a known control member assembly 24. Generally speaking, the control member assembly 24 includes the sealing surface 28 that engages a seating surface 31 of the seat ring 26 when the control member assembly 24 is in a closed position, thereby preventing the fluid from flowing through the valve body 12. More specifically, the control member assembly 24 further includes a tubular member 30 and a mounting subassembly 32. The tubular member 30 includes an upper end 30a and a lower end 30b that is open and accommodates the mounting subassembly 32. The mounting subassembly 32 further includes a mounting member 34, a plug or a disk holder 36 and a sealing disk 38 having the sealing surface 28.
The disk holder 36 includes the cylindrical body 37 having a flange 42 extending radially therefrom. The flange 42 includes a top surface 44 that abuts a bottom surface of the mounting member 34 (FIG. 1) and a bottom surface 46 that includes an annular recess 48 for receiving the sealing disk 38 having the sealing surface 28. The sealing disk 38 may include a generally ring-shaped disk made of a lower strength moldable resilient material, which is bonded to the disk holder 36 with an adhesive.
Generally speaking, lower strength moldable resilient sealing disks 38 degrade under high pressure drops and low flow conditions that are created at the interface of the sealing disk 38 and the seat ring 26. As a result, more robust materials may be used to form the sealing disk 38 for high pressure drops and low flow conditions. However, these more robust materials often lack sufficient bonding strength at high pressure drops and low flows, resulting in bonding failure between the disk holder 36 and the sealing disk 38, and, therefore, failure of the sealing disk 38 and the control member assembly 24 in general. More specifically, fluid impingement on the sealing disk 38 causes the bonding between the sealing disk 38 and the disk holder 36 to fail and/or may cause the sealing disk 38 to tear. Additionally, these more robust materials are more difficult to mold.